Synthesis, properties, and crystal and molecular structure of [Re2Br2(CO)6(Se2Ph2)], a binuclear rhenium(I) complex containing a diphenyl diselenide bridge

Abstract

The tetrahydrofuran (thf) adduct, [Re₂Br₂(CO)₆(thf)₂], reacts with diphenyl diselenide in toluene at room temperature to give the orange-red [Re₂Br₂(CO)₆(Se₂Ph₂)]. Three-dimensional X-ray analysis has shown this to be the first known example of a complex containing a Se₂R₂ unit bridging two metal atoms. The substance crystallises from toluene in the monoclinic system, space group C2/c with cell constants a= 11.813(3), b= 10.645(2), c= 19.593(5)Å, and β= 106.92(2)°, U= 2 357.15 ų, and D_c= 2.85 g cm^–3, M= 1 012.41 and Z= 4. Solution and refinement of the structure proved the compound to be isostructural with the diphenyl disulphide analogue reported previously and to consist of two Re^I atoms linked by two bromines and by a Se–Se bridge. The six carbonyl groups are distributed around the two rhenium atoms in two groups of three, each in a fac arrangement, thus completing the six co-ordination. The normals to the planes defined by Re(1)–Br(1)–Br(2) and by Re(2)–Br(1)–Br(2) intersect at an angle of 31°, a result which is similar to that found for the diphenyl disulphide, the dimethyl disulphide, and the tetraphenyldiphosphine derivatives. The Re–Se and Se–Se distances and the Re–Se–Se angle are 2.604(4) and 2.411(23)Å, and 106.2(1)°, respectively. The Re–Se–C(phenyl) angle is 109.9(8)°, while the Re ⋯ Re and Br ⋯ Br contacts are 3.90(4) and 3.462(20)Å. The Se(1) atom is 0.92 Å above the plane defined by Re(1)–Se(2)–C(phenyl) and the Re atoms are almost exactly in the plane defined by the two bromines and the two carbonyl carbon atoms; the torsional angle around the Se–Se bond is –121.4°. Similar to the dimethyl disulphide and the diphenyl disulphide derivatives, the diphenyl diselenide ligand of [Re₂Br₂(CO)₆(Se₂Ph₂)] is displaced by thf.